Co-extraction systems for separation and purification of butadiene and isoprene

ABSTRACT

Co-extraction techniques for separating and purifying butadiene and isoprene from a C 4  hydrocarbon mixture including butadiene and a C 5  hydrocarbon mixture including isoprene are provided. In an exemplary embodiment, a system includes a dimerization heat exchanger, a C 5  purification column; an extraction zone including a mainwasher column, a rectifier column and an afterwasher column; a distillation zone; a degassing zone; and an isoprene finishing column. The system can further include a C 5  washer column, an absorption column, and a distillation column.

CROSS REFERENCE TO RELATED APPLICATIONS

-   -   This application is a National Stage application of        PCT/IB2014/062458, WO 2014/203207, filed on Jun. 19, 2014, which        claims the benefit of U.S. Provisional Application No.        61/836,799, filed, Jun. 19, 2013, and U.S. Provisional        Application No. 61/929,677, filed Jan. 21, 2014, both of which        are incorporated by reference in their entirety herein.

FIELD

The presently disclosed subject matter relates to co-extraction systemsand processes for separating and purifying butadiene and isoprene fromC₄ and C₅ hydrocarbon mixtures.

BACKGROUND

Certain technologies for extracting isoprene from a C₅ hydrocarbonmixture and/or butadiene from a C₄ hydrocarbon mixture are known in theart. For example, U.S. Pat. No. 6,395,953 and U.S. Patent PublicationNo. 2008/0257711 disclose a process for producing a purified conjugateddiene (e.g., isoprene or butadiene) from a petroleum fraction (e.g., aC₄ hydrocarbon fraction or C₅ hydrocarbon fraction) by extractivedistillation. U.S. Pat. No. 4,310,388 describes a process for isolatinga conjugated diolefin from a C₄- or C₅-hydrocarbon mixture by extractivedistillation with the aid of a selective solvent. U.S. Pat. No.3,692,861 discloses a process for separating and purifying isoprene froma C₅ hydrocarbon fraction. U.S. Pat. No. 3,436,438 discloses a processof removing acetylenes from a hydrocarbon mixture containing conjugateddiolefins (e.g., isoprene or 1,3-butadiene) by using a solvent.

Two or more extraction systems can be required to extract both butadieneand isoprene, with resulting increases in capital cost, utilities, andland usage.

There remains a need in the art for a co-extraction system that canextract both butadiene and isoprene in one system rather than separatesystems.

SUMMARY

The presently disclosed subject matter provides co-extraction techniquesfor separating and purifying butadiene and isoprene from a C₄hydrocarbon mixture including butadiene and a C₅ hydrocarbon mixtureincluding isoprene. In an exemplary embodiment, a system includes a C₅purification column to receive a C₅ hydrocarbon mixture includingisoprene and separate the light ends of the C₅ hydrocarbon mixture fromthe heavy ends (C₅+) hydrocarbons. The system can further include anextraction zone, a distillation zone, a degassing zone, and an isoprenefinishing column to receive a crude isoprene product, where isoprene ispurified from the crude isoprene product.

In non-limiting embodiments of the presently disclosed subject matter,the extraction zone can include a mainwasher column to receive the lightends of the C₅ hydrocarbon mixture, a C₄ hydrocarbon mixture includingbutadiene, and an extractive solvent. Butadiene and isoprene can beco-extracted from the C₄ and C₅ hydrocarbon mixtures by using theextractive solvent to provide a crude butadiene product, C₄ acetylenes,and a crude isoprene product. The crude butadiene product can include1,3-butadiene and 1,2-butadiene, cis-2-butene, and trans-2-butene.1,3-butadiene can be present in a greater amount than 1,2-butadiene,cis-2-butene, and trans-2-butene. The crude isoprene product can includeisoprene and 1-pentene. Isoprene can be present in a greater amount than1-pentene. The extraction zone can also include a rectifier column toreceive the crude butadiene product, the crude isoprene product, theextractive solvent, and the C₄ acetylenes. The crude butadiene productcan be separated from the crude isoprene product, the extractive solventand the C₄ acetylenes in the rectifier column.

In certain embodiments, the extractive solvent can be an aqueoussolution of n-methyl 2-pyrrolidone having about 91.7% by weight ofn-methyl 2-pyrrolidone and about 8.3% by weight of water. In certainembodiments, the extraction zone can further include an afterwashercolumn coupled to the rectifier column to remove acetylene tracespresent in the crude butadiene product by using a solvent. The solventcan be n-methyl 2-pyrrolidone.

In non-limiting embodiments of the presently disclosed subject matter,the distillation zone includes a butadiene finishing column to receivethe crude butadiene product, where 1,3-butadiene is purified from thecrude butadiene product. In some embodiments, the crude butadieneproduct recovered from the afterwasher column includes propyne. Thus,the distillation zone can further include a propyne column coupled tothe afterwasher column to separate propyne from the crude butadieneproduct.

In non-limiting embodiments of the presently disclosed subject matter,the degassing zone includes a degasser column to receive the crudeisoprene product, the extractive solvent, and the C₄ acetylenes, wherethe extractive solvent is separated from the crude isoprene product andthe C₄ acetylenes. In some embodiments, the degassing zone can furtherinclude an acetylene washer column coupled to the degasser column toremove the extractive solvent from the crude isoprene product and the C₄acetylenes.

In certain embodiments the system can further include a selectivehydrogenation reactor for the C₄ acetylenes in the C₄ stream allocatedupstream of the butadiene extraction plant to convert acetylenes tobutadiene and 1-butene. Such a technology is already availablecommercially and provided by companies such as BASF, UOP and KBR.

In certain embodiments, the system can further include a dimerizationheat exchanger coupled to the C₅ purification column to dimerizecyclopentadiene present in the C₅ hydrocarbon mixture todicyclopentadiene. The system can also include a further hydrogenationreactor for converting the remaining undimerized cyclopentadiene tocyclopentene and cyclopentane.

The heavy ends (C₅+) hydrocarbons can include, e.g., dicyclopentadienepiperidine, cyclopentane, hexane, 1-hexene, 1,2-hexadiene,methyl-cyclopentadiene, benzene and cyclohexene. The light ends of theC₅ hydrocarbon mixture can include, e.g., pentane and isomers thereof,isoprene, pentadiene and isomers thereof, pentene and isomers thereof,and cyclopentene.

The system can further include a C₅ washer column that is coupled to thedownstream of the C₅ purification column. The C₅ washer column canreceive the light ends of the C₅ hydrocarbon mixture from the C₅purification column and an extractive solvent, where the extractivesolvent absorbs isoprene from the C₅ hydrocarbon mixture. The extractivesolvent can include an aqueous solution of n-methyl 2-pyrrolidone havingabout 91.7% by weight of n-methyl 2-pyrrolidone and about 8.3% by weightof water. The C₅ washer column can generate an overhead productincluding C₅ components that are not absorbed by the extractive solvent.The overhead product of the C₅ washer column can include C₅ alkanes(including pentane and isopentane), paraffins and C₅ mono-olefins(including pentene and isomers thereof). The C₅ washer column cangenerate a bottom product including the extractive solvent, acetylenes,and C₅ di-olefins, which can include pentadienes. The C₅ washer columncan generate a side product including isoprene. In certain embodiments,the side product of the C₅ washer column can further include C₅mono-olefins and di-olefins impurities.

The system can further include an absorption column that is coupled tothe downstream of the C₅ washer column. The C₅ washer column can receivean extractive solvent and the side product of the C₅ washer column,where isoprene along with C₅ mono-olefins is separated from C₅di-olefins with the aid of the extractive solvent in the absorptioncolumn. The extractive solvent can include an aqueous solution ofn-methyl 2-pyrrolidone having about 91.7% by weight of n-methyl2-pyrrolidone and about 8.3% by weight of water. The absorption columncan generate an overhead product including isoprene and C₅ mono-olefins,which can include cyclopentene and pentene isomers. The absorptioncolumn can generate a bottom product including C₅ diolefins.

The system can further include a distillation column that is coupled tothe downstream of the absorption column. The distillation column canreceive the overhead product of the absorption column, where isoprene isdistilled from the overhead product of the absorption column.

In accordance with another embodiment of the presently disclosed subjectmatter, processes for separating and purifying butadiene and isoprenefrom a C₄ hydrocarbon mixture including butadiene and a C₅ hydrocarbonmixture including isoprene are provided. The processes include feeding aC₅ hydrocarbon mixture including isoprene to a C₅ purification columnand separating the light ends of the C₅ hydrocarbon mixture from theheavy ends (C₅+) hydrocarbons in the C₅ purification column. Theprocesses can also include feeding the light ends of the C₅ hydrocarbonmixture, a C₄ hydrocarbon mixture including butadiene, and an extractivesolvent to a mainwasher column and co-extracting isoprene from the lightends of the C₅ hydrocarbon mixture and butadiene from the C₄ hydrocarbonmixture by using the extractive solvent in the mainwasher column toprovide a crude butadiene product, C₄ acetylenes, and a crude isopreneproduct. The extractive solvent can be an aqueous solution of n-methyl2-pyrrolidone having about 91.7% by weight of n-methyl 2-pyrrolidone andabout 8.3% by weight of water.

The processes can further include feeding the crude butadiene product,the crude isoprene product, the extractive solvent, and the C₄acetylenes to a rectifier column and separating the crude butadieneproduct from the crude isoprene product, the extractive solvent and theC₄ acetylenes in the rectifier column. In some embodiments, C₅impurities leave the rectifier column with the crude butadiene product.The C₅ impurities can include 1-pentene. Furthermore, the processes caninclude removing acetylene traces present in the crude butadiene productby using a solvent in an afterwasher column. In some embodiments, thecrude butadiene product recovered from the afterwasher column includespropyne. Thus, the process can include removing propyne from the crudebutadiene product in a propyne column. Furthermore, the processesinclude feeding the crude butadiene product to a butadiene finishingcolumn and purifying 1,3-butadiene from the crude butadiene product inthe butadiene finishing column. In some embodiments, the 1,3-butadienepurified from the butadiene finishing column can have a purity of atleast about 99.6% by weight.

In addition, the processes include feeding the crude isoprene product,the extractive solvent and the C₄ acetylenes to a degasser column, andseparating the extractive solvent from the crude isoprene product andthe C₄ acetylenes in the degasser column. The processes can also includeremoving the extractive solvent from the crude isoprene product and theC₄ acetylenes in an acetylene washer column. The processes furtherinclude feeding the crude isoprene product and the C₄ acetylenes to anisoprene finishing column and purifying isoprene from the crude isopreneproduct and the C₄ acetylenes in the isoprene finishing column. Theprocess can include operating the isoprene finishing column at a vacuumof about 50 kiloPascals (kPa) (0.5 atmosphere). In some embodiments, theisoprene purified from the isoprene finishing column has a purity ofabout 98.6% to about 99.6% by weight.

The processes can further include removing cyclopentadiene present inthe C₅ hydrocarbon mixture by dimerizing cyclopentadiene todicyclopentadiene in a dimerization heat exchanger. This can be followedby a selective hydrogenation reaction of the unconverted cyclopentadieneto cyclopentene and cyclopentane.

The process can further include feeding the light ends of the C₅hydrocarbon mixture from the C₅ purification column and an extractivesolvent to a C₅ washer column, where isoprene can be separated from theC₅ hydrocarbon mixture by the extractive solvent to generate an overheadproduct including C₅ components that are not absorbed by the extractivesolvent, a bottom product including the extractive solvent, C₅di-olefins, and acetylenes, and a side product including isoprene. Theside product of the C₅ washer column can include C₅ mono-olefins anddi-olefins impurities. The process can further include feeding the sideproduct of the C₅ washer column to an absorption column, where isoprenealong with C₅ mono-olefins can be separated from C₅ di-olefins with theaid of an extractive solvent to generate an overhead product includingisoprene and C₅ mono-olefins and a bottom product including C₅ diolefinsand the extractive solvent including the solvent fed to the C₅ washercolumn. The process can further include feeding the overhead product ofthe absorption column to a distillation column, where isoprene can bedistilled from the overhead product of the absorption column.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a co-extraction system for separating and purifyingbutadiene and isoprene in accordance with one non-limiting exemplaryembodiment of the disclosed subject matter.

FIG. 2 shows a process for separating and purifying butadiene andisoprene in accordance with one non-limiting exemplary embodiment of thedisclosed subject matter.

FIG. 3 shows a co-extraction system for separating and purifyingbutadiene and isoprene in accordance with one non-limiting exemplaryembodiment of the disclosed subject matter.

FIG. 4 shows a process for separating and purifying butadiene andisoprene in accordance with one non-limiting exemplary embodiment of thedisclosed subject matter.

DETAILED DESCRIPTION

The presently disclosed subject matter provides co-extracting systemsand processes for separating and purifying butadiene and isoprene from aC₄ hydrocarbon mixture including butadiene and a C₅ hydrocarbon mixtureincluding isoprene.

The term “about” or “substantially” means within an acceptable errorrange for the particular value as determined by one of ordinary skill inthe art, which will depend in part on how the value is measured ordetermined, i.e., the limitations of the measurement system. Forexample, “about” can mean a range of up to 20%, up to 10%, up to 5%, andor up to 1% of a given value.

As used herein, the term “co-extracting,” “co-extraction,” or“co-extracted” means extracting or extraction of at least two materialsor compounds in one process or in one extractive distillation column.For example, the presently disclosed subject matter provides aco-extraction system for butadiene and isoprene, where butadiene andisoprene are extracted in one extractive distillation column, e.g., amainwasher column.

While technologies for separating and purifying butadiene or isoprenefrom a C₄ or C₅ hydrocarbon mixture are known in the art, at least twoextraction plants or systems are required to extract both butadiene andisoprene. It is not known in the art to co-extract butadiene andisoprene in one system. The presently disclosed systems and processescan co-extract butadiene and isoprene. Moreover, the extracted butadieneand isoprene have a high purity, e.g., at least about 99.6% by weight,or about 98.6% to about 99.6% by weight.

For the purpose of illustration and not limitation, FIG. 1 shows aco-extraction system 1 in accordance with one embodiment of thedisclosed subject matter. FIG. 2 shows a co-extracting process inaccordance with one embodiment of the disclosed subject matter. As shownin FIG. 1, the co-extraction system 1 includes a heattreatment/hydrogenation reactor 2. As shown in FIGS. 1 and 2, a C₅hydrocarbon mixture including isoprene is fed to the heattreatment/hydrogenation reactor 2. A C₅ hydrocarbon mixture can includeisoprene, trans- and cis-1,3-pentadiene, cyclopentadiene (DCPD) asconjugated diolefins, together with pentanes, n-pentenes, isoamylene,cyclopentene, higher acetylenes, methyl pentane isomers, piperyleneisomers and methyl cyclobutane. A thermal dimerization is carried outand cyclopentadiene present in the C₅ hydrocarbon mixture is dimerizedto form di-cyclopentadiene in the heat treatment/hydrogenation reactor2. The dimerization reaction can be conducted at a temperature of about90° C. to about 130° C. using medium pressure steam and a pressure ofabout 100 kPa to about 900 kPa (about 1 barg to about 9 barg). The C₅hydrocarbon mixture is heated in the dimerization heat exchanger forabout 5 to about 200 minutes. A substantial amount of cyclopentadiene,e.g., at least about 92% by weight, is removed in this process.Optionally, a further selective hydrogenation can follow to convert anyremaining cyclopentadiene to cyclopentene and cyclopentane as discussedin, for example, U.S. Pat. Nos. 3,439,060 and 4,471,153. Therefore allcyclopentadiene present in C₅ stream can be converted todicyclopentadiene, cyclopentene and cyclopentane. Optionally, thehydrogenation reactor 2 can be placed after the C₅ purification column.

Example processes for removing cyclopentadiene present in a C₅hydrocarbon mixture by thermal dimerization are disclosed, for example,in U.S. Pat. Nos. 2,768,224, 2,971,036, and 3,692,861. In order toobtain very pure isoprene that is suitable for polymerization topolyisoprene, it can be important to remove cyclopentadiene from a C₅hydrocarbon mixture because cyclopentadiene has a poisoning effect uponthe so-called Ziegler-type catalyst and retards polymerization. Inaddition, cyclopentadiene can clog downstream columns or boilers in theextractive distillation zone if it dimerizes to dicyclopentadiene. TheC₅ hydrocarbon mixture can be obtained by thermal cracking of apetroleum fraction, e.g., Liquefied Petroleum Gases (“LPG”), naphtha andthe like.

As shown in FIGS. 1 and 2, the C₅ hydrocarbon mixture is then fed to aC₅ purification column 3, where the heavy ends (C₅+) hydrocarbons 20 andthe light ends of the C₅ hydrocarbon mixture 22 are separated. Forexample, the heavy ends (C₅+) hydrocarbons 20 leave from a bottom 24,and the light ends of the C₅ hydrocarbon mixture leave from an overheador top 26, of the C₅ purification column 3. Heavy ends (C₅+)hydrocarbons include dicyclopentadiene, piperidine, cyclopentane,hexane, 1-hexene, 1,2-hexadiene, methyl-cyclopentadiene, benzene andcyclohexene. Certain C₅ hydrocarbons, e.g., piperidine and cyclopentane,can be separated with hydrocarbons having 6 or more carbon atoms fromisoprene, because their boiling points are higher than isoprene's. Lightends of a C₅ hydrocarbon mixture include pentane and isomers thereof,isoprene, pentene (e.g., 1-pentene) and isomers thereof, pentane andisomers thereof (e.g., isopentane), pentadiene and isomers thereof, andcyclopentene.

As shown in FIGS. 1 and 2, the light ends of the C₅ hydrocarbon mixtureincluding isoprene enter an extraction zone 4. The extraction zone 4 caninclude a mainwasher column 5 and a rectifier column 6. The light endsof the C₅ hydrocarbon mixture including isoprene enter the mainwashercolumn from its top 28. In the C₄, stream an optional selectivehydrogenation reactor for C₄ acetylene can be installed upstream toconvert these components to butadiene and 1-butenes using commerciallyavailable technologies. A C₄ hydrocarbon mixture including butadieneenters the mainwasher column 5 from its bottom 30. The C₄ hydrocarbonmixture can be obtained by thermal cracking of a petroleum fraction,e.g., LPG, naphtha and the like. A C₄ hydrocarbon mixture can includebutanes, 1-butene, isobutene, vinylacetylene, ethylacetylene and1,2-butadiene, 1,3-butadiene, isobutane, trans-2-butene, cis-2-butene,1-butyne, and small amounts of C₃ hydrocarbons, such as propane, propyneand propadiene, and/or C₅ hydrocarbons such as isopentane. In themainwasher column 5, butadiene and isoprene are co-extracted from the C₄hydrocarbon mixture and the C₅ hydrocarbon mixture, respectively, withthe aid of an extractive solvent, thereby generating a crude butadieneproduct and a crude isoprene produce. Acetylenes (e.g., vinylacetyleneand ethylacetylene) are also extracted from the C₄ hydrocarbon mixturein the mainwasher column 5 by the extractive solvent, and are referredto as “C₄ acetylenes.”

The extractive solvent can be conventional solvents, e.g.,N-alkyl-substituted cyclic aliphatic acid amides (lactams) having 5 ringmembers, e.g., N-alkylpyrrolidones (e.g., n-methyl 2-pyrrolidone(“NMP”)), acetonitrile, dimethylformamide, acetone, furfural,butyrolactone, furfuraldehyde, methoxypropionitrile, N-alkyl-substitutedlower aliphatic acid amides, e.g., dimethylformamide, diethylformamide,dimethylacetamide, diethylacetamide and formylmorpholine. In oneembodiment, the extractive solvent is NMP or an aqueous solution of NMP.NMP, especially an aqueous NMP solution, can be superior to otherconventional solvents, because it is non-toxic, non-carcinogenic, andcan be treated by conventional biological waste water treatment. Inaddition, an aqueous NMP solution is non-corrosive, thereby allowing theuse of carbon steel as construction material without the need for acorrosion inhibitor. NMP also has low solvent losses due to itsresistance to hydrolysis and thermal decomposition as well as its highboiling point, and thus, there will be no vapor losses. Furthermore, NMPis less expensive than other extractive solvents. An aqueous solution ofNMP can contain up to 15% by weight of water. In one embodiment, theextractive solution is an aqueous solution of NMP including about 91.7%by weight of NMP and about 8.3% by weight of water.

In some embodiments, the extraction zone 4 includes a flash vessel 15,as shown in FIG. 1. The C₄ hydrocarbon mixture can be vaporized in theflash vessel 15 before entering the mainwasher column 5, as shown inFIGS. 1 and 2. The C₄ hydrocarbon mixture in gas phase is passed throughthe mainwasher column 5 counter-currently to the aqueous NMP solution.For extracting 1,3-butadiene from a C₄ hydrocarbon mixture, NMP can actas an absorbent over various absorption and desorption stages. Forexample, 1,3-butadiene is absorbed by NMP while the butenes and butanespresent in a C₄ hydrocarbon mixture remain in the gas phase. As such,1,3-butadiene is separated from butenes and butanes. The overheadproduct of the mainwasher column 5 includes butenes and butanes and isdesignated as Raffinate-1. The flow rate of the aqueous NMP solution canbe adjusted to minimize the amount of 1,3-butadiene in the overheadproduct (e.g., Raffinate-1) of the mainwasher column 5, e.g., about 0.1%to about 0.2% by weight of 1,3-butadiene in the overhead product. Acrude butadiene product, the extractive solvent (e.g., NMP), and C₄acetylenes (e.g., vinylacetylene and ethylacetylene) leave themainwasher column 5 from its bottom 30. The crude butadiene productincludes 1,3-butadiene and its isomers, e.g., 1,2-butadiene. In someembodiments, the crude butadiene product may include small amounts of C₄impurities, e.g., cis-2-butene and trans-2-butene. Processes andtechnologies for using NMP to extract butadiene from a C₄ hydrocarbonmixture are disclosed, e.g., in U.S. Pat. Nos. 4,310,388, and 6,337,429,and German Patent Publication No. DE 2724365, each of which is herebyincorporated by reference in its entirety.

For extracting isoprene from a C₅ hydrocarbon mixture, the light ends ofthe C₅ hydrocarbon mixture in liquid phase with a temperature close tothat of the extractive solvent (e.g., aqueous NMP solution) enters themainwasher column 5 from its top 28, as shown in FIG. 2. The light endsof the C₅ hydrocarbon mixture are passed through the mainwasher column 5co-currently to the aqueous NMP solution. Isoprene is extracted from thelight ends of C₅ hydrocarbon mixture by the extractive solvent (e.g.,aqueous NMP solution). A crude isoprene product including isopreneleaves the mainwasher column 5 from its bottom 30. In some embodiments,the crude isoprene product may include a small amount of C₅ impurities,e.g., 1-pentene. The C₅ hydrocarbons that are not extracted by theextractive solvent, including mainly pentane, isopentane and partly1-pentene, are stripped from the mainwasher column 5 by the risingvapors of the C₄ hydrocarbon mixture. The unextracted C₅ hydrocarbonsleave the mainwasher column 5 from its top as part of the overheadproduct of the mainwasher column 5. The flow rate of the aqueous NMPsolution can be adjusted to minimize the amount of isoprene in theoverhead product of the mainwasher column 5, e.g., about 0.2% to 0.6% byweight of isoprene in the overhead product.

The crude isoprene product, the crude butadiene product, the extractivesolvent and C₄ acetylenes leave from the bottom 30 of the mainwashercolumn 5, and enter a rectifier column 6, as shown in FIGS. 1 and 2. Inthe rectifier column 6, the crude butadiene product is separated fromthe crude isoprene product, the extractive solvent, and the C₄acetylenes. The crude butadiene product leaves the rectifier column 6 ingas phase as a side draw stream. Most of the C₅ impurities (e.g.,1-pentene) leave the rectifier column 6 with the crude butadieneproduct. The C₄ acetylenes, the crude isoprene product and theextractive solvent, with or without traces of C₅ impurities (e.g.,1-pentene) leave the rectifier column 6 from its bottom 32 and enter adegassing zone 8, as shown in FIGS. 1 and 2. Therefore, the crudebutadiene product and the crude isoprene product are separated in therectifier column 6.

The extraction zone 4 can further include an afterwasher column 7. Afterleaving the rectifier column 6, the crude butadiene product in gas phasecan be fed to an afterwasher column 7 to remove acetylene traces thatmay escape with the crude butadiene product in the side draw stream fromthe rectifier column 6 by a fresh aqueous NMP solution having about91.7% of NMP and about 8.3% of water. The fresh aqueous NMP solution canbe fed to a top 34 of the afterwasher column 7. The crude butadieneproduct is recovered in the overhead product of the afterwasher column7. In some embodiments, the overhead product of the afterwasher column 7includes propyne that is an impurity present in a C₄ hydrocarbonmixture. NMP solvent is not present in the overhead due to its highboiling point.

The crude butadiene product enters a distillation zone 9 for furtherpurification. In certain embodiments, the distillation zone 9 includes apropyne column 10. In the propyne column 10, propyne and the crudebutadiene product are separated. Propyne is removed as overhead from thepropyne column 10 and the crude butadiene product leaves the propynecolumn 10 from its bottom 36 and enters a butadiene finishing column 11,as shown in FIGS. 1 and 2. In the butadiene finishing column 11,1,3-butadiene is withdrawn from a top 38 of the column 11 and butadieneisomers (e.g., 1,2-butadiene) as well as other C₄ impurities (e.g.,trans-2-butene and cis-2-butene) are rejected in the bottom of thecolumn 36. In some embodiments, small amounts of C₅ impurities (mainly1-pentene) and traces of isoprene are rejected in a bottom 40 of anisoprene finishing column 14. A highly pure 1,3-butadiene can beproduced in the butadiene finishing column 11. In some embodiments, thepurified 1,3-butadiene has a purity of at least 99% by weight, e.g., atleast about 99.6% by weight.

The C₄ acetylenes, the crude isoprene product and the extractivesolvent, with or without traces of C₅ impurities (e.g., 1-pentene) leavethe rectifier column 6 from its bottom and enter a degassing zone 8, asshown in FIGS. 1 and 2. The degassing zone 8 can include a degassercolumn 12. The extractive solvent is separated from the crude isopreneproduct and C₄ acetylenes in the degasser column 12. The extractivesolvent leaves the degasser column 12 from its bottom 42. The extractivesolvent can be recycled to the extraction zone 4. The crude isopreneproduct reduces polymerization of acetylene by diluting theconcentration of acetylene in the degasser column 12, which is operatedat a higher temperature than other columns in certain embodiments. Incertain embodiments, the degassing zone 8 can include an acetylenewasher column 13, as shown in FIGS. 1 and 2. The crude isoprene productand C₄ acetylenes, with or without traces of C₅ impurities (e.g.,1-pentene), leave the degasser column 12 as a side draw stream in gasphase and enter an acetylene washer column 13, as shown in FIGS. 1 and2. The acetylene washer column 13 further removes any extractivesolvent, which may escape with the crude isoprene and C₄ acetylenes fromthe degasser column 12. In one example, water is added to a top 44 ofthe acetylene washer column 13 to absorb the extractive solvent into aliquid phase, which is withdrawn from a bottom 46 of the column 13. Thecrude isoprene product and C₄ acetylenes, with or without traces of C₅impurities (e.g., 1-pentene), are dewatered in successive settlingvessels, and are fed to an isoprene finishing column 14, as shown inFIGS. 1 and 2. In the isoprene finishing column 14, isoprene isseparated from C₄ acetylenes and C₅ impurities (e.g., 1-pentene). C₄acetylenes and C₅ impurities leave as the overhead product of theisoprene finishing column 14. C₄ acetylenes can be hydrogenated and usedas fuel gas or as cracker feed, or burned in a flare system. Isoprene iswithdrawn from the bottom 40 of the isoprene finishing column 14. Ahighly pure isoprene is produced in the isoprene finishing column 14. Insome embodiments, the purified isoprene has a purity of about 98.6% to99.6% by weight. The isoprene finishing column 14 can be operated undera vacuum of about 0.5 atmosphere to avoid polymerization of acetylenesand isoprene.

In some embodiments, the system can include an isoprene polishing column(not shown) to obtain a higher purified isoprene, e.g., isoprene with apurity of greater than 99.6% by weight. Isoprene can be separated fromother heavy hydrocarbons (e.g., dimerized dienes such as traces ofdicyclopentadiene and venylcyclohexene) in the isoprene polishingcolumn. The isoprene polishing column can be operated under the samevacuum as that for the isoprene finishing column.

Additionally or alternatively, the system can include a C₅ washer column16. For the purpose of illustration and not limitation, FIGS. 3 and 4show an exemplary system and a process in accordance with anotherembodiment of the disclosed subject matter, respectively. As shown inFIGS. 3 and 4, crude C₅ can enter a heat exchanger/hydrogenation reactor82 and exit as a C₅ hydrocarbon and enter a C₅ purification column 3with the light ends of the C₅ hydrocarbon mixture including isopreneproduced or separated from the C₅ purification column 3 as shown inFIGS. 1 and 2 can enter a C₅ washer column 16 at about the middle of thecolumn as vapor. An extractive solvent 56 can be introduced to a top 50of the C₅ washer column 16 as liquid to absorb the isoprene from the C₅vapors. The extractive solvent can include an aqueous solution ofn-methyl 2-pyrrolidone having about 91.7% by weight of n-methyl2-pyrrolidone and about 8.3% by weight of water.

As shown in FIG. 3, the C₅ washer column 16 can be fitted with acondenser and a reboiler. The overhead from the C₅ washer column can beraffinate stream that includes C₅ components that are not absorbed bythe extractive solvent, including alkanes (e.g., pentane, isopentane),paraffins and mono-olefins (e.g., pentene (e.g., 1-penetene) and isomersthereof). The bottom product of the C₅ washer column can include theextractive solvent along with di-olefins (e.g., pentadienes) and certainacetylenes. An isoprene rich stream 52 can be taken out of the side ofthe C₅ washer column 16 at a location below the middle of the C₅ washercolumn 16 by a vapor draw off stream.

The vapor draw of isoprene can enter an absorption column (17 in FIGS. 3and 4) close to the bottom tray, and a fresh feed of NMP 54 can beintroduced to a top 56 of the column 17. The absorption column 17 can befitted with a reboiler 70 and a condenser 72. In the absorption column17, isoprene along with certain mono-olefins such as cyclopentene andcertain pentene isomers can be separated from impurities of di-olefinscarried in the vapor phase with the isoprene by the fresh solvent fedfrom the top 58 of this column 17. This extract that includes diolefinsand extractive solvent can leave the bottom 60 of the absorption column17 and can be returned back to the C₅ washer column 16. The isoprenealong with the remaining C₅ hydrocarbon mixture can be withdrawn fromthe overhead of the absorption column 17 and can enter a distillationcolumn (18 in FIGS. 3 and 4). In the distillation column 18, isoprenecan be separated out as the light component from the remaining C₅components, which are heavier than isoprene and can leave thedistillation column 18 from its bottom 62. This stream can be remixedwith the Pygas aromatic stream of C₆+. The purity of the isopreneoverhead product can be about 99 wt % or more, e.g., in a range of fromabout 99.0 wt % to about 99.9 wt %. The column 18 overhead pressure isclose to atmospheric and is preferably about 20 kPa to about 100 kPa(about 0.2 barg to about 1 barg).

The bottom stream 74 from the C₅ washer column 16 at about 160° C. canbe used to heat the boilers 70 of the absorption column 17 and thedistillation column 18, and can be used to heat up the propyne columnboiler downstream of the butadiene plant, which can save separationenergy and ensure heat integration in the butadiene plant. Afterreleasing its heat, the bottom stream 74 from the C₅ washer column 16can then be further cooled to about 38° C. to about 45° C. and can becombined with the extractive solvent stream that is recycled from thebutadiene plant and can enter the mainwasher column 5 from the top 28.

C₄ impurities can be separated from C₅ di-olefins components based ontheir selectivity in the extractive solvent. The C₅ components can enterthe rectifier column. As shown in FIGS. 1 and 2, the crude isopreneproduct (C₅ components) along with the C₄ acetylenes can be carried inthe extractive solvent to the degasser column. As shown in FIGS. 1 and2, in the degasser column, the C₄ acetylenes and the crude isopreneproduct (C₅ components, which include primarily diolefins, e.g.,pentadienes isomers) are drawn off as vapor stream out of the extractivesolvent. The bottom product of the degasser column can include theextractive solvent that is free of hydrocarbons and can be recycled backas fresh extractive solvent feed. Part of the recycled extractivesolvent feed can be used for extracting the C₅ hydrocarbon mixture asdescribed above, and then can rejoin the other extractive solvent feedbefore it enters the mainwasher column 5 of the butadiene plant.

EXAMPLES

The following examples are merely illustrative of the presentlydisclosed subject matter and they should not be considered as limitingthe scope of the presently disclosed subject matter in any way.

Example 1

A commercially available process simulation software tool (PRO-II) wasused to construct an in-house model describing the process embodimentsgiven in this disclosure. Process simulation software tools forchemicals processes are known to one of ordinary skill in the art. Thein-house model constructed has been used successfully to simulatebutadiene extraction process by using an aqueous NMP solution in onebutadiene plant. The in-house model was used to simulate the process ofco-extraction of butadiene and isoprene in the same plant as describedabove and as shown in FIGS. 1 and 2.

The in-house model was verified against butadiene extraction plant datawhere an isoprene spike in the C₄ hydrocarbon feed stream to amainwasher column was measured at different locations around the plant.The results were compared with the model results as shown in Table 1where isoprene percent level in butadiene plant was taken as 100 unitsof measure in the feed to the mainwasher column. The results show thatthe plant data and the results from the model prediction were fairlycomparable. This finding consolidates the workable schemes of theembodiments given in the disclosure which are based on simulation modelresults.

TABLE 1 Isoprene level in downstream units to isoprene in feed to amainwasher column Column Plant data Model prediction Acetylene washercolumn overhead 80% 88.5% Mainwasher column overhead  8% 6.4%Afterwasher column overhead 5.4%  5.1%

The results of certain selected streams with main components by usingthe simulation model are shown in Table 2.

TABLE 2 Stream Composition Wet Bases C₄ C₅ Butadiene Isoprenehydrocarbon hydrocarbon Overhead purified purified mixture mixtureOverhead product of from a from an fed to a fed to a product of a anbutadiene isoprene mainwasher mainwasher mainwasher afterwasherfinishing finishing column column column column column column Components(wt %) (wt %) (wt %) (wt %) (wt %) (wt %) propyne 0.0316 0.0375propadiene 3.6429E−03 butane 5.8969 11.6103 isobutane 1.2072 2.37681-butene 12.5472 24.7040 isobutene 14.7248 0.1829 29.0449 trans-2-6.8850 13.5556 butene cis-2-butene 3.2380 6.2308 0.1282 0.05421,3-butadiene 53.7831 0.2000 93.0610 99.8241 1,2-butadiene 0.1752 0.25260.0821 1-butyne 0.1323 vinylacetylene 0.8051 pentane 24.9004 7.2805isoprene 43.9165 0.5349 0.5766 98.8350 1-pentene 26.5482 1.7506 5.3298isopentane 0.5401 4.4479 2.3639 butadiene 0.0251 0.4521 dimers

Example 2

The simulation model used in Example 1 was applied to obtain results forthe process as depicted shown in FIGS. 3 and 4 to simulateisoprene/butadiene co-extraction using an aqueous NMP. The results ofcertain selected streams with main components are shown in Table 3below.

TABLE 3 Stream Composition C₅ Bottom Feed to Isoprene hydrocarbonOverhead product of C₅ absorption 1 from purified from mixture fed toproduct of washer column vapor draw of absorption a C₅ washer a C₅washer going to main- C₅ washer column 2 column column washer columncolumn overhead Components (wt %) (wt %) (wt %) (wt %) (wt %) 1-butene2.4637 3.4453 isobutene 0.6358 0.8891 trans-2-butene 0.3576 0.5001cis-2-butene 0.3576 0.5001 1,3-butadiene 10.3318 14.4478 0.9713 1.8987pentane 36.7966 51.4557 isoprene 15.8949 0.8335 62.0872 99.95481-pentene 2.4637 3.4451 isopentane 16.2130 22.6720 neopentane 0.15900.2223 Trans2-pentene 0.3576 0.4998 1.5838E−03 2.5183E−03 Cis2-pentene0.3576 0.4999 3.3610E−03 5.1660E−03 1,2-pentadiene 4.7266 1.3125E−03Cis-1,3-pentadiene 2.5410 2.9865E−06 0.4582 5.7895 Trans1,3-pentadiene2.5419 2.6229E−06 0.4587 10.9696 cyclopentene 3.8011 3.4060E−04 16.6834NMP 90.0218 Water 8.0832

The systems and methods disclosed herein include at least the followingembodiments:

Embodiment 1

A co-extraction system for separating and purifying butadiene andisoprene from a C₄ hydrocarbon mixture comprising butadiene and a C₅hydrocarbon mixture comprising isoprene, comprising: (a) a C₅purification column to receive a C₅ hydrocarbon mixture comprisingisoprene and separate the light ends of the C₅ hydrocarbon mixture fromthe heavy ends (C₅+) hydrocarbons; (b) an extraction zone, comprising:(i) a mainwasher column to receive the light ends of the C₅ hydrocarbonmixture, a C₄ hydrocarbon mixture comprising butadiene, and anextractive solvent, wherein butadiene and isoprene are co-extracted fromthe C₄ and C₅ hydrocarbon mixtures by using the extractive solvent toprovide a crude butadiene product, C₄ acetylenes, and a crude isopreneproduct; and (ii) a rectifier column to receive the crude butadieneproduct, the crude isoprene product, the extractive solvent, and the C₄acetylenes, wherein the crude butadiene product is separated from thecrude isoprene product, the extractive solvent, and the C₄ acetylenes;(c) a distillation zone, comprising a butadiene finishing column toreceive the crude butadiene product, wherein 1,3-butadiene is purifiedfrom the crude butadiene product; (d) a degassing zone, comprising adegasser column to receive the crude isoprene product, the extractivesolvent, and the C₄ acetylenes, wherein the extractive solvent isseparated from the crude isoprene product and the C₄ acetylenes; and (e)an isoprene finishing column to receive the crude isoprene product andthe C₄ acetylenes, wherein isoprene is purified from the crude isopreneproduct and the C₄ acetylenes.

Embodiment 2

The system of embodiment 1, wherein the extractive solvent comprises anaqueous solution of n-methyl 2-pyrrolidone having about 91.7% by weightof n-methyl 2-pyrrolidone and about 8.3% by weight of water.

Embodiment 3

The system of embodiment 1 or embodiment 2, further comprising adimerization heat exchanger coupled to the C₅ purification column todimerize cyclopentadiene present in the C₅ hydrocarbon mixture todicyclopentadiene.

Embodiment 4

The system of any of embodiments 1 to 3, wherein the crude butadieneproduct comprises 1,3-butadiene, 1,2-butadiene, cis-2-butene, andtrans-2-butene.

Embodiment 5

The system of embodiment 4, wherein 1,3-butadiene is present in agreater amount than 1,2-butadiene, cis-2-butene, and trans-2-butene.

Embodiment 6

The system of any of embodiments 1 to 5, wherein the crude isopreneproduct comprises isoprene and 1-pentene.

Embodiment 7

The system of embodiment 6, wherein isoprene is present in a greateramount than 1-pentene.

Embodiment 8

The system of any of embodiments 1 to 7, the extraction zone furthercomprises (iii) an afterwasher column coupled to the rectifier column toremove acetylene traces present in the crude butadiene product by usinga solvent.

Embodiment 9

The system of embodiment 8, wherein the solvent is n-methyl2-pyrrolidone.

Embodiment 10

The system of embodiment 8, wherein the crude butadiene productrecovered from the afterwasher column comprises propyne.

Embodiment 11

The system of embodiment 8, wherein the distillation zone furthercomprises a propyne column coupled to the afterwasher column to separatepropyne from the crude butadiene product.

Embodiment 12

The system of any of embodiments 1 to 11, wherein the degassing zonefurther comprises an acetylene washer column coupled to the degassercolumn to remove the extractive solvent from the crude isoprene productand the C₄ acetylenes.

Embodiment 13

The system of any of embodiments 1 to 12, wherein the heavy ends (C₅+)hydrocarbons comprise piperidine, cyclopentane, hexane, 1-hexene,1,2-hexadiene, methyl-cyclopentadiene, benzene and cyclohexene.

Embodiment 14

The system of embodiment 13, wherein the heavy ends (C₅+) hydrocarbonscomprise dicyclopentadiene.

Embodiment 15

The system of any of embodiments 1 to 14, wherein the light ends of theC₅ hydrocarbon mixture comprise pentane and isomers thereof, isoprene,pentene and isomers thereof, pentadiene and isomers thereof, andcyclopentene.

Embodiment 16

The system of any of embodiments 1 to 15, further comprising a C₅ washercolumn that is coupled to the downstream of the C₅ purification columnand receives the light ends of the C₅ hydrocarbon mixture from the C₅purification column and an extractive solvent, wherein the extractivesolvent absorbs isoprene from the C₅ hydrocarbon mixture.

Embodiment 17

The system of embodiment 16, wherein the extractive solvent comprises anaqueous solution of n-methyl 2-pyrrolidone having about 91.7% by weightof n-methyl 2-pyrrolidone and about 8.3% by weight of water.

Embodiment 18

The system of embodiment 16, wherein the C₅ washer column generates anoverhead product comprising C₅ components that are not absorbed by theextractive solvent.

Embodiment 19

The system of embodiment 18, wherein the overhead product of the C₅washer column comprises C₅ alkanes, paraffins and C₅ mono-olefins.

Embodiment 20

The system of embodiment 19, wherein the C₅ mono-olefins comprisespentene and isomers thereof.

Embodiment 21

The system of embodiment 19, wherein the C₅ alkanes comprises pentaneand isopentane.

Embodiment 22

The system of embodiment 16, wherein the C₅ washer column generates abottom product comprising the extractive solvent, C₅ di-olefins, andacetylenes.

Embodiment 23

The system of embodiment 22, wherein the di-olefins comprisespentadienes.

Embodiment 24

The system of embodiment 16, wherein the C₅ washer column generates aside product comprising isoprene.

Embodiment 25

The system of embodiment 24, wherein the side product of the C₅ washercolumn further comprises C₅ mono-olefins and di-olefins impurities.

Embodiment 26

The system of embodiment 25, further comprising an absorption columnthat is coupled to the downstream of the C₅ washer column and receivesan extractive solvent and the side product of the C₅ washer column,wherein isoprene along with C₅ mono-olefins is separated from C₅di-olefins with the aid of the extractive solvent in the absorptioncolumn.

Embodiment 27

The system of embodiment 26, wherein the extractive solvent comprises anaqueous solution of n-methyl 2-pyrrolidone having about 91.7% by weightof n-methyl 2-pyrrolidone and about 8.3% by weight of water.

Embodiment 28

The system of embodiment 26, the absorption column generates an overheadproduct comprising isoprene and C₅ mono-olefins.

Embodiment 29

The system of embodiment 28, wherein the mono-olefins comprisescyclopentene and pentene isomers.

Embodiment 30

The system of embodiment 26, wherein the absorption column generates abottom product comprising C₅ diolefins and the extractive solvent.

Embodiment 31

The system of embodiment 28, further comprising a distillation columnthat is coupled to the downstream of the absorption column and receivesthe overhead product of the absorption column, wherein isoprene isdistilled from the overhead product of the absorption column.

Embodiment 32

A process for separating and purifying butadiene and isoprene from a C₄hydrocarbon mixture comprising butadiene and a C₅ hydrocarbon mixturecomprising isoprene, comprising: feeding a C₅ hydrocarbon mixturecomprising isoprene to a C₅ purification column; separating the lightends of the C₅ hydrocarbon mixture from the heavy ends (C₅+)hydrocarbons in the C₅ purification column; feeding the light ends ofthe C₅ hydrocarbon mixture, a C₄ hydrocarbon mixture comprisingbutadiene, and an extractive solvent to a mainwasher column;co-extracting isoprene from the light ends of the C₅ hydrocarbon mixtureand butadiene from the C₄ hydrocarbon mixture by using the extractivesolvent in the mainwasher column to provide a crude butadiene product,C₄ acetylenes, and a crude isoprene product; feeding the crude butadieneproduct, the crude isoprene product, the extractive solvent, and the C₄acetylenes to a rectifier column; separating the crude butadiene productfrom the crude isoprene product, the extractive solvent and C₄acetylenes in the rectifier column; feeding the crude butadiene productto a butadiene finishing column; purifying 1,3-butadiene from the crudebutadiene product in the butadiene finishing column; feeding the crudeisoprene product, the extractive solvent and the C₄ acetylenes to adegasser column; separating the extractive solvent from the crudeisoprene product and the C₄ acetylenes in the degasser column; feedingthe crude isoprene product and the C₄ acetylenes to an isoprenefinishing column; and purifying isoprene from the crude isoprene productand the C₄ acetylenes in the isoprene finishing column.

Embodiment 33

The process of embodiment 32, wherein the extractive solvent comprisesan aqueous solution of n-methyl 2-pyrrolidone having about 91.7% byweight of n-methyl 2-pyrrolidone and about 8.3% by weight of water.

Embodiment 34

The process of embodiment 32 or embodiment 33, further comprisingremoving cyclopentadiene present in the C₅ hydrocarbon mixture bydimerizing cyclopentadiene to dicyclopentadiene in a dimerization heatexchanger.

Embodiment 35

The process of any of embodiments 32 to 34, further comprising removingcyclopentadiene present in the C₅ hydrocarbon mixture by selectivehydrogenation of cyclopentadiene to cyclopentene and cyclopentane.

Embodiment 36

The process of any of embodiments 32 to 35, further comprising a C₄selective hydrogenation reactor for acetylenes present in the C₄ streamupstream of the butadiene extraction plant.

Embodiment 37

The process of any of embodiments 32 to 36, further comprising removingacetylene traces present in the crude butadiene product by using asolvent in an afterwasher column.

Embodiment 38

The process of any of embodiments 32 to 37, further comprisingseparating propyne from the crude butadiene product in a propyne column.

Embodiment 39

The process of any of embodiments 32 to 38, further comprising removingthe extractive solvent from the crude isoprene product and the C₄acetylenes in an acetylene washer column.

Embodiment 40

The process of any of embodiments 32 to 39, wherein the 1,3-butadienepurified in the butadiene finishing column has a purity of at leastabout 99.6% by weight.

Embodiment 41

The process of any of embodiments 32 to 40, wherein the isoprenepurified in the isoprene finishing column has a purity of about 98.6% toabout 99.6% by weight.

Embodiment 42

The process of any of embodiments 32 to 42, comprising operating theisoprene finishing column at a vacuum of about 0.5 atmosphere.

Embodiment 43

The process of any of embodiments 32 to 42, further comprising feedingthe light ends of the C₅ hydrocarbon mixture from the C₅ purificationcolumn and an extractive solvent to a C₅ washer column.

Embodiment 44

The process of embodiment 43, further comprising absorbing isoprene fromthe C₅ hydrocarbon mixture by the extractive solvent in the C₅ washercolumn to generate an overhead product comprising C₅ components that arenot absorbed by the extractive solvent, a bottom product comprising theextractive solvent, C₅ di-olefins, and acetylenes, and a side productcomprising isoprene.

Embodiment 45

The process of embodiment 43, wherein the side product of the C₅ washercolumn comprises C₅ mono-olefins and di-olefins impurities.

Embodiment 46

The process of embodiment 44, further comprising feeding the sideproduct of the C₅ washer column and an extractive solvent to anabsorption column.

Embodiment 47

The process of embodiment 46, further comprising separating isoprenealong with C₅ mono-olefins from C₅ di-olefins with the aid of theextractive solvent in the absorption column to generate an overheadproduct comprising isoprene and C₅ mono-olefins and a bottom productcomprising C₅ diolefins and extractive solvent.

Embodiment 48

The process of embodiment 47, further comprising feeding the overheadproduct of the absorption column to a distillation column.

Embodiment 49

The process of embodiment 48, further comprising distilling isoprenefrom the overhead product of the absorption column in the distillationcolumn.

Although the presently disclosed subject matter and its advantages havebeen described in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the presently disclosed subject matter asdefined by the appended claims. Moreover, the scope of the presentlydisclosed subject matter is not intended to be limited to the particularembodiments of the process, machine, manufacture, and composition ofmatter, means, methods and steps described in the specification. As oneof ordinary skill in the art will readily appreciate from the disclosureof the presently disclosed subject matter, processes, machines,manufacture, compositions of matter, means, methods, or steps, presentlyexisting or later to be developed that perform substantially the samefunction or achieve substantially the same result as the correspondingembodiments described herein can be utilized according to the presentlydisclosed subject matter. Accordingly, the appended claims are intendedto include within their scope such modifications.

What is claimed is:
 1. A co-extraction system for separating andpurifying butadiene and isoprene from a C₄ hydrocarbon mixturecomprising butadiene and a C₅ hydrocarbon mixture comprising isoprene,comprising: (a) a C₅ purification column to receive a C₅ hydrocarbonmixture comprising isoprene and separate the light ends of the C₅hydrocarbon mixture from the heavy ends (C₅+) hydrocarbons; (b) anextraction zone, comprising: (i) a mainwasher column to receive thelight ends of the C₅ hydrocarbon mixture, a C₄ hydrocarbon mixturecomprising butadiene, and an extractive solvent, wherein butadiene andisoprene are co-extracted from the C₄ and C₅ hydrocarbon mixtures byusing the extractive solvent to provide a crude butadiene product, C₄acetylenes, and a crude isoprene product; and (ii) a rectifier column toreceive the crude butadiene product, the crude isoprene product, theextractive solvent, and the C₄ acetylenes, wherein the crude butadieneproduct is separated from the crude isoprene product, the extractivesolvent, and the C₄ acetylenes; (c) a distillation zone, comprising abutadiene finishing column to receive the crude butadiene product,wherein 1,3-butadiene is purified from the crude butadiene product; (d)a degassing zone, comprising a degasser column to receive the crudeisoprene product, the extractive solvent, and the C₄ acetylenes, whereinthe extractive solvent is separated from the crude isoprene product andthe C₄ acetylenes; and (e) an isoprene finishing column to receive thecrude isoprene product and the C₄ acetylenes, wherein isoprene ispurified from the crude isoprene product and the C₄ acetylenes.
 2. Thesystem of claim 1, wherein the extractive solvent comprises an aqueoussolution of n-methyl 2-pyrrolidone having about 91.7% by weight ofn-methyl 2-pyrrolidone and about 8.3% by weight of water.
 3. The systemof claim 1, further comprising a dimerization heat exchanger coupled tothe C₅ purification column to dimerize cyclopentadiene present in the C₅hydrocarbon mixture to dicyclopentadiene.
 4. The system of claim 1,wherein the crude butadiene product comprises 1,3-butadiene,1,2-butadiene, cis-2-butene, and trans-2-butene and wherein the crudeisoprene product comprises isoprene and 1-pentene.
 5. The system ofclaim 1, the extraction zone further comprises (iii) an afterwashercolumn coupled to the rectifier column to remove acetylene tracespresent in the crude butadiene product by using a solvent.
 6. The systemof claim 1, wherein the degassing zone further comprises an acetylenewasher column coupled to the degasser column to remove the extractivesolvent from the crude isoprene product and the C₄ acetylenes.
 7. Thesystem of claim 1, wherein the heavy ends (C₅+) hydrocarbons comprisepiperidine, cyclopentane, hexane, 1-hexene, 1,2-hexadiene,methyl-cyclopentadiene, benzene and cyclohexene and wherein the lightends of the C₅ hydrocarbon mixture comprise pentane and isomers thereof,isoprene, pentene and isomers thereof, pentadiene and isomers thereof,and cyclopentene.
 8. The system of claim 1, further comprising a C₅washer column that is coupled to the downstream of the C₅ purificationcolumn and receives the light ends of the C₅ hydrocarbon mixture fromthe C₅ purification column and an extractive solvent, wherein theextractive solvent absorbs isoprene from the C₅ hydrocarbon mixture. 9.The system of claim 8, wherein the C₅ washer column generates anoverhead product comprising C₅ components that are not absorbed by theextractive solvent wherein the overhead product of the C₅ washer columncomprises C₅ alkanes, paraffins and C₅ mono-olefins and wherein the C₅washer column generates a bottom product comprising the extractivesolvent, C₅ di-olefins, and acetylenes.
 10. The system of claim 8,further comprising an absorption column that is coupled to thedownstream of the C₅ washer column and receives an extractive solventand the side product of the C₅ washer column, wherein isoprene alongwith C₅ mono-olefins is separated from C₅ di-olefins with the aid of theextractive solvent in the absorption column.
 11. The system of claim 10,the absorption column generates an overhead product comprising isopreneand C₅ mono-olefins and wherein the C₅ washer column generates a bottomproduct comprising the extractive solvent, C₅ di-olefins, andacetylenes.
 12. The system of claim 11, further comprising adistillation column that is coupled to the downstream of the absorptioncolumn and receives the overhead product of the absorption column,wherein isoprene is distilled from the overhead product of theabsorption column.
 13. A process for separating and purifying butadieneand isoprene from a C₄ hydrocarbon mixture comprising butadiene and a C₅hydrocarbon mixture comprising isoprene, comprising: feeding a C₅hydrocarbon mixture comprising isoprene to a C₅ purification column;separating the light ends of the C₅ hydrocarbon mixture from the heavyends (C₅+) hydrocarbons in the C₅ purification column; feeding the lightends of the C₅ hydrocarbon mixture, a C₄ hydrocarbon mixture comprisingbutadiene, and an extractive solvent to a mainwasher column;co-extracting isoprene from the light ends of the C₅ hydrocarbon mixtureand butadiene from the C₄ hydrocarbon mixture by using the extractivesolvent in the mainwasher column to provide a crude butadiene product,C₄ acetylenes, and a crude isoprene product; feeding the crude butadieneproduct, the crude isoprene product, the extractive solvent, and the C₄acetylenes to a rectifier column; separating the crude butadiene productfrom the crude isoprene product, the extractive solvent and C₄acetylenes in the rectifier column; feeding the crude butadiene productto a butadiene finishing column; purifying 1,3-butadiene from the crudebutadiene product in the butadiene finishing column; feeding the crudeisoprene product, the extractive solvent and the C₄ acetylenes to adegasser column; separating the extractive solvent from the crudeisoprene product and the C₄ acetylenes in the degasser column; feedingthe crude isoprene product and the C₄ acetylenes to an isoprenefinishing column; and purifying isoprene from the crude isoprene productand the C₄ acetylenes in the isoprene finishing column.
 14. The processof claim 13, further comprising removing cyclopentadiene present in theC₅ hydrocarbon mixture by dimerizing cyclopentadiene todicyclopentadiene in a dimerization heat exchanger.
 15. The process ofclaim 13, further comprising removing cyclopentadiene present in the C₅hydrocarbon mixture by selective hydrogenation of cyclopentadiene tocyclopentene and cyclopentane.
 16. The process of claim 13, furthercomprising separating propyne from the crude butadiene product in apropyne column.
 17. The process of claim 13, further comprising removingthe extractive solvent from the crude isoprene product and the C₄acetylenes in an acetylene washer column.
 18. The process of claim 13,further comprising feeding the light ends of the C₅ hydrocarbon mixturefrom the C₅ purification column and an extractive solvent to a C₅ washercolumn.
 19. The process of claim 18, further comprising absorbingisoprene from the C₅ hydrocarbon mixture by the extractive solvent inthe C₅ washer column to generate an overhead product comprising C₅components that are not absorbed by the extractive solvent, a bottomproduct comprising the extractive solvent, C₅ di-olefins, andacetylenes, and a side product comprising isoprene.